The invention relates to a method and device for removing at low pressures water vapor from a water vapor containing medium, particularly from a stripper steam for stripping edible oils at low pressures.
It is commonly known to use steam for deacidulation and deodorization by continuous distillation, of edible oils at very low pressures for example of less than the pressure of a 4 mm mercury column. For the continuous removal of the water vapor containing medium, obtained by thus treating edible oils from an apparatus, systems are used so far, comprising steam jet pumps and condensors. The steam containing medium with a very low pressure is brought to a higher pressure in the steam jet pumps, whilst adding driving steam, whereupon the mixture is introduced into condensors after which the products obtained in the shape of water and non-condensable material are discharged by means of pumps.
The driving steam increasing the pressure of the steam containing medium is commensurate to the quantity of the water vapor containing medium to be discharged and depends on the ratio of the pressures before or beyond the steam jet pump or pumps.
When oils are continuously deacidulated and deodorized by distillation at very low pressures of e.g. less than the pressure of a 4 mm mercury column, much steam is required consequently to bring the steam containing medium, coming from the deacidulating and deodorizing treatment by means of distillation to such a pressure that this steam can be condensed by for instance cooling water. The quantity of cooling water required for condensing the steam is very great, however.
Apart from this disadvantage of high operation costs of steam, cooling water, discharge and electricity for pumps, considerable investments are required for steam jet pumps, condensors and pumps.
Besides, a very important disadvantage of these systems consists in that they cause considerable environment pollution, since the water vapor containing medium, obtained by refining edible oils at low pressures, always contains impurities coming from the oil, like e.g. traces of fatty acids, flavouring substances and undesired odor-diffusing substances and the like, which are introduced together with the operative steam from the steam jet pumps into the condensors.
The impurities are likewise condensed by the cooling water in the condensors, so that the large quantities of water leaving the condensors in the form of cooling water with condensed driving steam and condensed stripper steam, are polluted by impurities which, though small in quantity, are intolerable, however. The discharge costs of this polluted water are very high and will presumably get higher in the future. Therefore much interest is excited by a method and device by which environment pollution is avoided and water consumption is decreased e.g. by using an apparatus capable of absorbing water vapor containing medium at low pressures. Some absorption agents with a low partial tension are known in the art, which are capable of absorbing water vapor at low pressures, like e.g. brines. Such absorption means suffer, however, from the disadvantage that their application field is very limited, while moreover their process should be carefully controlled. Finally the investments for such systems are considerable, so that said systems are of no importance in practice.